Observations of two spheres suspended from the terminals of a high voltage generator remind us of the principles that opposite charges attract, like charges repel, and uncharged bodies have no electric interaction. To determine quantitatively the effect of distance on electric force, a sensitive balance measures the force between two charged spheres. The distance is varied and the electric force is calculated from changes in balance readings. A graph of electric force against distance suggests the equation Fr^2 = k (a constant), and the tabulated data confirm this relation. To illustrate the applications in chemistry of these principles, the migration of positive and negative ions in an electric field and their mutual precipitation are shown in time-lapse photography and in animation.
Science Consultants: Prof. J. Leland Hollenberg, University of Redlands, Redlands, California, and Prof. J. Arthur Campbell, Harvey Mudd College, Claremont, California.
Wardâs Volume 8, CHEM Study #4109, 17 1/2 minutes. In color, 1989.